Fisher Space Pen with a Uni Style + Fit Refill

In terms of pocket-carry writers, the Fisher Space Pen is a great solution: small, made with quality materials, rounded ends (so as not to put a hole in the pocket) and has a dependable assembly
but
the FSP standard cartridge (and refill) are not the best for conditions outside of the "extreme".

Saying "not the best" may actually be a vast understatement.  Since the beginning of using these pens, I have had great dissatisfaction with the line quality. Really this is quite a shame because the pen design is so damn great
then
 whilst swiping through my Instagram following last week I come across the brilliant hack with the modification of the Uni Style + Fit refill into the Fisher Space Pen.

With this Instagram image acting as a catalyst, I had reached that moment when I could no longer put off the move to get more out of my FSP. A quick internet search on FSP refill hacks uncovered a number of sources that went through the possibilities. The results fortified my determination to do it as soon as possible. Even though there are many possibilities, I decided to go with the one that the Instagram image promoted, The Uni Style + Fit .038.

A side by side shot of the Fisher refill (bottom pen) with the Uni refill (top pen) reveal the end results.

Fisher Space Pen with a Uni Style + Fit 0.38 refill.

Fisher Space Pen with a Uni Style + Fit 0.38 refill.

Below is a detail of the Fisher Space Pen refill.
A very dependable writer in more extreme of conditions. This pen is great for taking hunting, camping or wherever there is excessive dirt (sawdust) or water. The line quality may be poor but there is no denying its dependability. If one needs to take a note this cartridge will get the job done.

Below is a detail of the Fisher with the Uni .38 refill.
During any particular day, I prefer to pocket-carry at least two different line widths: A detailing line and a broader or a more expressionistic line. In general, this preference was accomplished with a compact fountain pen and a sharp bullet pencil. 

now
 I can add a very compact .38 gel tip in a FSP to my carry with very little to no burden.
 I will add here, it will not replace my bullet pencil. It remains important to carry both pencil and pen as much as it does to carry a detail and a broader lined writer. So now I have three essential EDC writers.
I am good with that.

Fisher Space Pen with a Uni Style + Fit 0.38 refill.

Fisher Space Pen with a Uni Style + Fit 0.38 refill.

The simple 3 part process:
1. disassemble the FSP and lay its standard cartridge next to the Uni Style + Fit refill.
2. the Uni Style is a bit longer than the FSP cartridge so trim to the same length
3. insert into the pen and join the two barrel halves for a dry run. (Actually, I had to trim a fraction more off of the Uni Style refill for a "best" fit length).

Now technically a person can stop here. That is all there is to it.
The compression alone will keep everything nice and firm,
however
There is something about the thinness of the Uni Style's cartridge outer diameter (o.d.) that bothered me. The FSP cartridge tapers out about 1/3 of the way up for a better fit in the barrels inner diameter (i.d.).

A short length of electrical tape around the Uni Style made fast work of approximating the same o.d. as FSP. Now I can call this complete.

Fisher Space Pen with a Uni Style + Fit 0.38 refill.

Fisher Space Pen with a Uni Style + Fit 0.38 refill.

I still have one more Fisher Space Pen to play with I think I will be converting that to another .38 but in red or green.